1. Field of the Invention
The present invention relates to a printed circuit board. More specifically, the present invention relates to a printed circuit board that is disposed in a lens barrel with an imaging optical system, or disposed in a lens barrel provided with a ring-shaped motor.
2. Related Art Statement
There are various flexible printed boards proposed for use within a lens barrel having an imaging optical system. For example, Japanese Patent Application Laid-Open No. 63-166293 (1988) discloses a technique in which a flexible printed circuit (FPC) board having a nearly-ring-shaped portion is disposed at an end portion of a lens barrel so that electrical components may be mounted on the above-described nearly-ring-shaped portion. In this technique, protruding portions such as mounts for the connection to other components are formed on the nearly-ring-shaped portion.
U.S. Pat. No. 4,990,948 discloses a technique in which electric components are mounted on a band-shaped FPC board and then this FPC board is bent in the direction parallel to the optical axis so as to form a polygon, and finally the FPC board is put into a polygon-shaped case along the inner wall faces. However, in the above-mentioned techniques disclosed in Japanese Patent Application Laid-Open No. 63-166293(1988) and U.S. Pat. No. 4,990,948, when the FPC-board is disposed in a lens barrel with a lens, if the diameter of the optical path associated with the lens is large, then the area of the FPC-board must be reduced, which results in limitation in a space available for the mounting of electrical components or for electrical interconnections. As a result, a large extent of modifications in interconnection routing is required, and in some cases, it will be impossible to make interconnection between some components.
Another problem in the conventional techniques is that there is a need to provide portions for making electrical connection to other external components, which causes an increase in complexity of the connecting processes and also causes an increase in the area of the FPC-board, which in turn causes an increase in cost. Furthermore, in the technique disclosed in U.S. Pat. No. 4,990,948, because an FPC-board has a form of a band, if the number of components to be mounted on the FPC-board is increased, these mounted components take the area required for electrical interconnections, which makes it difficult to achieve high density mounting of components. Furthermore, the lengths of interconnections along circumferential paths between end portions become long, which causes a reduction in the efficiency of the interconnection design.
Various techniques have also been proposed for the arrangement of electrical components on a printed circuit board disposed in a lens barrel in which a ring-shaped motor such as an ultrasonic motor is used as a driving power source.
For example, in a conventional printed circuit board, as shown in perspective views of FIGS. 11 and 12 which illustrate arrangements of major elements of a lens barrel, a donut-shaped printed circuit board (referred to as a PC hereinafter) 101 or 102 is disposed at a rear side (in the case of FIG. 11) or at a front side (in the case of FIG. 12) of a ring-shaped motor or an ultrasonic motor (referred to as an USM hereinafter) 104 that is disposed within a frame 103 of a lens barrel in a fashion that the USM 104 is coaxial with respect to the optical axis O, so as to achieve a high space-efficiency arrangement. In the PCs 101 and 102 shown in FIGS. 11 and 12, electrical components such as integrated circuits 101a, 102a, and resistors 101b, 102b are mounted on the respective PCs 101 and 102.
In another conventional technique for arranging electrical components on the printed circuit board, as shown in perspective views of FIGS. 13 and 14 which illustrate arrangements of major elements of lens barrel, a polygon-shaped barrel FPC 111 or 112 that has been bent to form a shape of a polygon is disposed at a rear side (in the case of FIG. 13) or at a front side (in the case of FIG. 14) of a USM 114 that is disposed within a frame 113 of a lens barrel in a fashion that the USM 114 is coaxial with respect to the optical axis O, so as to achieve a high space-efficiency arrangement. In the abovedescribed PCs 111 and 112 shown in FIGS. 13 and 14, electrical components such as integrated circuits 111a and 112a, and resistors 111b and 112b are mounted on respective PCs 111 and 112.
In still another conventional technique for arranging electrical components, as shown in a perspective view of FIG. 15 which illustrate an arrangement of major elements, a polygon-shaped barrel FPC 121 that has been bent to form a shape of a polygon is disposed around the outer periphery of a USM 124 that is disposed within a frame 123 of a lens barrel in a fashion that the USM 124 is coaxial with respect to the optical axis O, so as to achieve a high space-efficiency arrangement. In the PC 121 shown in FIG. 15, electrical components such as an integrated circuit 121a and a resistor 121b are also mounted on the PC 121.
However, in the above-described conventional techniques shown in FIGS. 11-14 for arranging electrical components on a printed circuit board for use in a lens barrel, there is a problem that a large length is required for lens frames 103 and 113 due to the manner of arrangement in which PCs 101, 102 or PCs 111, 112 are disposed at a front or rear side of USMs 104, 114.
In the case of the conventional technique shown in FIG. 15, a space around the outer periphery of the USM 124 is required for disposing the FPC 121, and thus there is a problem that the outer dimension of the lens barrel becomes large.